I'm having the same issue after installing the current version. (I never used the previous version.) I've added the "Posts In Sidebar" widget to my sidebar. When I expand the options, select a single tag from the drop-down menu, the selected tag populates the tag field. I then hit "save". After I hit "save", the tag field reverts back to "any".

Please let me know if there's any additional information I could provide to help troubleshoot the issue and thanks!